Enhanced Transmission Selection (ETS) is a network scheduler scheduling algorithm that has been defined by the Data Center Bridging Task Group of the IEEE 802.1 Working Group. [1] It is a hierarchical scheduler that combines static priority scheduling and a bandwidth sharing algorithms (such as Weighted round robin or Deficit round robin).
The Enhanced Transmission Selection algorithm is one scheduling algorithm supported by IEEE 802.1Q. In Enhanced Transmission Selection, they are two types or queues: Strict priority or Credit-based queues, and bandwidth-assigned queues. Each bandwidth-assigned queue has a bandwidth parameter, and the total for all bandwidth-assigned queue must be 100%. [2] [3] [4] [5]
If there is no frame ready for transmission, in the Strict priority and Credit-based queues, a frame from the bandwidth-assigned queue can be transmitted. A bandwidth-sharing algorithm is in charge of selecting the queue such that the bandwidth consumed by each queue approaches its percentage of the bandwidth leftover by the Strict priority and Credit-based queues. If a queue uses less than its percentage, the remainder of its percentage used by other queues.
The standard does not specify which bandwidth-sharing algorithm must be used since there are a number of variants of bandwidth sharing algorithm, but gives some constraints and references Weighted round robin. The Linux implementation of ETS does not consider Credit-based queues and uses Deficit round robin as bandwidth-sharing algorithm. ETS is also implemented in Microsoft Network Drivers [6]
Carrier-sense multiple access (CSMA) is a media access control (MAC) protocol in which a node verifies the absence of other traffic before transmitting on a shared transmission medium, such as an electrical bus or a band of the electromagnetic spectrum.
Round-robin (RR) is one of the algorithms employed by process and network schedulers in computing. As the term is generally used, time slices are assigned to each process in equal portions and in circular order, handling all processes without priority. Round-robin scheduling is simple, easy to implement, and starvation-free. Round-robin scheduling can be applied to other scheduling problems, such as data packet scheduling in computer networks. It is an operating system concept.
IEEE 802.11e-2005 or 802.11e is an approved amendment to the IEEE 802.11 standard that defines a set of quality of service (QoS) enhancements for wireless LAN applications through modifications to the media access control (MAC) layer. The standard is considered of critical importance for delay-sensitive applications, such as Voice over Wireless LAN and streaming multimedia. The amendment has been incorporated into the published IEEE 802.11-2007 standard.
Network congestion in data networking and queueing theory is the reduced quality of service that occurs when a network node or link is carrying more data than it can handle. Typical effects include queueing delay, packet loss or the blocking of new connections. A consequence of congestion is that an incremental increase in offered load leads either only to a small increase or even a decrease in network throughput.
Weighted round robin (WRR) is a network scheduler for data flows, but also used to schedule processes.
Deficit Round Robin (DRR), also Deficit Weighted Round Robin (DWRR), is a scheduling algorithm for the network scheduler. DRR is, like weighted fair queuing (WFQ), a packet-based implementation of the ideal Generalized Processor Sharing (GPS) policy. It was proposed by M. Shreedhar and G. Varghese in 1995 as an efficient and fair algorithm.
Resilient Packet Ring (RPR), also known as IEEE 802.17, is a protocol standard designed for the optimized transport of data traffic over optical fiber ring networks. The standard began development in November 2000 and has undergone several amendments since its initial standard was completed in June 2004. The amended standards are 802.17a through 802.17d, the last of which was adopted in May 2011. It is designed to provide the resilience found in SONET/SDH networks but, instead of setting up circuit oriented connections, provides a packet based transmission, in order to increase the efficiency of Ethernet and IP services.
Generalized processor sharing (GPS) is an ideal scheduling algorithm for process schedulers and network schedulers. It is related to the fair-queuing principle which groups packets into classes and shares the service capacity between them. GPS shares this capacity according to some fixed weights.
In computer science, an input queue is a collection of processes in storage that are waiting to be brought into memory to run a program. Input queues are mainly used in Operating System Scheduling which is a technique for distributing resources among processes. Input queues, not only apply to operating systems (OS), but may also be applied to scheduling inside networking devices. The purpose of scheduling is to ensure resources are being distributed fairly and effectively; therefore, it improves the performance of the system.
Fair queuing is a family of scheduling algorithms used in some process and network schedulers. The algorithm is designed to achieve fairness when a limited resource is shared, for example to prevent flows with large packets or processes that generate small jobs from consuming more throughput or CPU time than other flows or processes.
Bandwidth management is the process of measuring and controlling the communications on a network link, to avoid filling the link to capacity or overfilling the link, which would result in network congestion and poor performance of the network. Bandwidth is described by bit rate and measured in units of bits per second (bit/s) or bytes per second (B/s).
Weighted fair queueing (WFQ) is a network scheduling algorithm. WFQ is both a packet-based implementation of the generalized processor sharing (GPS) policy, and a natural extension of fair queuing (FQ). Whereas FQ shares the link's capacity in equal subparts, WFQ allows schedulers to specify, for each flow, which fraction of the capacity will be given.
Stream Reservation Protocol (SRP) is an enhancement to Ethernet that implements admission control. In September 2010 SRP was standardized as IEEE 802.1Qat which has subsequently been incorporated into IEEE 802.1Q-2011. SRP defines the concept of streams at layer 2 of the OSI model. Also provided is a mechanism for end-to-end management of the streams' resources, to guarantee Quality of Service (QoS).
Multipath routing is a routing technique simultaneously using multiple alternative paths through a network. This can yield a variety of benefits such as fault tolerance, increased bandwidth, or improved security.
Credit-based fair queuing is a computationally efficient alternative to fair queueing. Credit is accumulated to queues as they wait for service. Credit is spent by queues while they are being serviced. Queues with positive credit are eligible for service. The rate of credit accumulation and release can be adjusted on a queue-by-queue basis to produce a weighted queuing behavior.
The Time-Triggered Ethernet standard defines a fault-tolerant synchronization strategy for building and maintaining synchronized time in Ethernet networks, and outlines mechanisms required for synchronous time-triggered packet switching for critical integrated applications, IMA and integrated modular architectures. SAE International has released SAE AS6802 in November 2011.
Data center bridging (DCB) is a set of enhancements to the Ethernet local area network communication protocol for use in data center environments, in particular for use with clustering and storage area networks.
A network scheduler, also called packet scheduler, queueing discipline, qdisc or queueing algorithm, is an arbiter on a node in packet switching communication network. It manages the sequence of network packets in the transmit and receive queues of the network interface controller. There are several network schedulers available for the different operating systems, that implement many of the existing network scheduling algorithms.
Time-Sensitive Networking (TSN) is a set of standards under development by the Time-Sensitive Networking task group of the IEEE 802.1 working group. The TSN task group was formed in November 2012 by renaming the existing Audio Video Bridging Task Group and continuing its work. The name changed as a result of the extension of the working area of the standardization group. The standards define mechanisms for the time-sensitive transmission of data over deterministic Ethernet networks.
Deterministic Networking (DetNet) is an effort by the IETF DetNet Working Group to study implementation of deterministic data paths for real-time applications with extremely low data loss rates, packet delay variation (jitter), and bounded latency, such as audio and video streaming, industrial automation, and vehicle control.